Direction-1 is the direction of the flow through the porous media, and direction-2 is the normal.
Enter the given viscous and inertial coefficients for Direction-1 and enter a higher value of the coefficients (my practice is 100 times) for direction-2.
This means that you are increasing the resistance to the flow in the normal direction and giving the right amount of resistance in the flow direction.
I hope i made myself clear

Regards
Luke

Note: Do not use the velocity formulations unles you're what it means and if you need it.

I am trying to model a oscillatory flow(fluid will move back and forth from heat exchanger at the rate of oscillation 300Hz) through the heat exchanger of very small size. For that I am considering or modeled heat exchanger as a porous media and I want to maintain the temperature of heat exchanger at 600 K and gas temperature is less than the heat exchanger temperature. So, heat will flow from heat exchanger porous material to the gas.

For this situation, I am modelling compressible flow (I think, I should use Density based solver...?) through porous media. But during the input of porous media in fluent "Fixed Value" option is not working when density based solver is activated. It is only working with Pressure based solver.

Any one can guide me on this.........? How can I set the constant temperature of porous media while using density based solver?